Demand for transportation fuels coupled with increased crude prices and deteriorating quality have forced refiners for enhancing liquid yields at the same time decrease the yield of undesired products like coke and dry gas. Delayed Coker is one of the major non-catalytic work horse of refining industry for the production of LPG, olefinic naphtha, diesel and heavy oil operating on the principle of free radical mechanism with rejection of coke. The delayed coking process has evolved with many improvements since the mid-1930s. Delayed coking is a semi-continuous process in which the heavy feedstock is heated to a high temperature. The first patent for this technology is U.S. Pat. No. 1,831,719, which discloses cracking of the hot vapor mixture in the coking receptacle before its temperature falls below 950° F. The heavy residua feed is thermally cracked in the drum to produce lighter hydrocarbons and solid, petroleum coke. This process is conducted in batches with operation time of 6-12 hrs. The main concern of refining industry is higher batch time cycle and higher coke yield. There have been continuous efforts in enhancing liquid yield with reduction in coke. In delayed coking, substantial amount of volatile matter still remains on coke which determines the overall economy of the process. The hardness of coke can be a rough measure of efficiency of the process. Lower the volatile material in the petroleum coke, higher the hardness and thus higher liquid yields. Various petroleum coke uses have specifications with volatile matter less than 12 wt %. The note worthy commercial processes which focuses towards reduction in volatile matter the coke are Fluid coking and Flexi coking developed by Exxon Mobil. Fluid Coking®, developed since the late 1950s, is a continuous coking process that uses fluidized solids to increase the conversion of coking feedstocks to cracked liquids, and further reduce the volatile content of the product coke, In Fluid Coking®, the coking feedstock blend is sprayed into a fluidized bed of hot, fine coke particles in the reactor. Heat for the endothermic cracking reactions is supplied by the hot particles, this permits the cracking and coking reactions to be conducted at higher temperatures (about 480-565° C.) and shorter contact times than in delayed coking. The Fluid Coking technology reduces the volatile combustible matter within 4-10wt %. Flexicoking® is an improvement of the Fluid Coking® process, in which a third major vessel is added to gasify the product coke.
Heavy Oil and bitumen are supplementing the decline in the production of conventional light and medium crude oil, and production from these resources is expected to dramatically increase. Presently, heavy oil and bitumen are made transportable by addition of diluents. However, diluted feedstock's are different from conventional crude oils. As a results, bitumen blends or synthetic crudes are not easily processed in conventional fluid catalytic cracking process. Therefore in either of cases refiner must be configured to handle either diluted or upgraded feedstock.
Many heavy hydrocarbon feedstocks are also characterized as comprising significant amounts of BS&W (bottom sediment and water). Such feedstocks are not suitable for transportable by pipeline, or upgrading due to the sand, water and corrosive properties of the feedstock. Typically, feedstocks characterized as having less than 0.5 wt. % BS&W are transportable by pipeline, and those comprising greater amount of BS&W require some degree of processing and treatment to reduce the BS&W content prior to transport. Such processing may include storage to let the water and particulates settle, followed by heat treatment to drive of water and other components. However, these manipulations are expensive and time consuming There is therefore a need within the art for an efficient method for upgrading feedstock comprising a significant BS&W content prior to transport or further processing of the feedstock.
Heavy oils and bitumens can be upgraded using a range of rapid processes including thermal (e.g., U.S. Pat. Nos. 4,490,243; 4,294,686; and 4,161,442), hydrocracking (U.S. Pat. No. 4,252,634) visbreaking (U.S. Pat. Nos. 4,427,539; 4,569,753; and 5,413,702) or catalytic cracking (U.S. Pat. Nos. 5,723,040; 5,662,868; 5,296,131; 4,985,136; 4,772,378; 4,668,378, and 4,578,183) procedures. Several of these processes, such as visbreaking or catalytic cracking, utilize either inert or catalytic particulate contact materials within upflow or downflow reactors. Catalytic contact materials are for the most part zeolite based (see for example U.S. Pat. Nos. 5,723,040; 5,662,868; 5,296,131; 4,985,136; 4,772,378; 4,668,378, 4,578,183; 4,435,272; and 4,263,128), while visbreaking typically utilizes inert contact material (e.g., U.S. Pat. Nos. 4,427,539; and 4,569,753), carbonaceous solids (e.g., U.S. Pat. No. 5,413,702), or inert kaolin solids (e.g., U.S. Pat. No. 4,569,753).
The use of fluid catalytic cracking (FCC), or other, units for the direct processing of bitumen feedstocks is known in the art. However, many compounds present within the crude feedstocks interfere with these processes by depositing on the contact material itself. These feedstock contaminants include metals such as vanadium and nickel, coke precursors such as Conradson carbon and asphaltenes, and sulfur, and the deposit of these materials results in the requirement for extensive regeneration of the contact material. This is especially true for contact material employed with FCC processes as efficient cracking and proper temperature control of the process requires contact materials comprising little or no combustible deposit materials or metals that interfere with the catalytic process.
To reduce contamination of the catalytic material within catalytic cracking units, pretreatment of the feedstock via visbreaking (U.S. Pat. Nos. 5,413,702; 4,569,753; and 4,427,539), thermal (U.S. Pat. Nos. 4,252,634; and 4,161,442) or other processes, typically using FCC-like reactors, operating at temperatures below that required for cracking the feedstock (e.g. U.S. Pat. Nos. 4,980,045; and 4,818,373 and U.S. Pat. No. 4,263,128;) have been suggested. These systems operate in series with FCC units and function as pre-treaters for FCC. These pretreatment processes are designed to remove contaminant materials from the feedstock, and operate under conditions that mitigate any cracking This ensures that any upgrading and controlled cracking of the feedstock takes place within the FCC reactor under optimal conditions.
Several of these processes (e.g. U.S. Pat. Nos. 4,818,373; 4,427,539; 4,311,580; 4,232,514; and 4,263,128;) have been specifically adapted to process “resids” (i.e. feedstocks produced from the fractional distillation of a whole crude oil) and bottom fractions, in order to optimize recovery from the initial feedstock supply. The disclosed processes for the recovery of resids, or bottom fractions, are physical and involve selective vaporization or fractional distillation of the feedstock with minimal or no chemical change of the feedstock. These processes are also combined with metals removal and provide feedstocks suitable for FCC processing. The selective vaporization of the resid takes place under non-cracking conditions, without any reduction in the viscosity of the feedstock components, and ensures that cracking occurs within an FCC reactor under controlled conditions. None of these approaches disclose the upgrading of feedstock within this pretreatment (i.e. metals and coke removal) process. Other processes for the thermal treatment of feedstocks involve hydrogen addition (hydrotreating) which results in some chemical change in the feedstock.
U.S. Pat. No. 4,378,288 relates a process for increasing coker distillate yield in a coking process by adding a small amount, generally 0.005-10% by weight of a free radical inhibitor selected from the group consisting of hydroquinone and N-phenyl-2-naphthylamine to the coker feed material.
U.S. Pat. No. 4,832,823 refers to an improved coking process is described wherein a feedstock comprising residual oil is passed into a coking zone along with a highly aromatic oil such as pyrolysis tars or a decanted oil produced from a fluidized catalytic cracking zone in a concentration resulting in the feedstock having from about 5 to about 20 percent by weight of highly aromatic oil. The yield of coke is thereby reduced.
U.S. Pat. No. 5,039,390 is directed to a composition and methods for controlling undesirable coke formation and deposition commonly encountered during the high temperature processing of hydrocarbons. Coke formation can be inhibited by adding a sufficient amount of a combination of a boron compound and a dihydroxyphenol.
U.S. Pat. No. 5,853,565 provides a method for controlling the relative proportion of products produced from a petroleum residuum by thermal coking. Coke yield promoting compounds are identified, and effective attenuating agents are specified. The method can mitigate a coke promoting effect induced by certain surfactants, antifoulants, or fugitive catalysts in thermal coking units. Mitigating the coke yield promoting effect of molybdenum, for example, in a thermal coker permits recovery of a greater proportion of distillate boiling range products.
U.S. Pat. No. 6,860,985 relates to a method for improving yield in petroleum streams derived from coking processes in flexicoking & fluidcoking. In a preferred embodiment, the invention relates to a method for regenerating filters employed to remove particulate matter from coker gas oil to improve coker gas oil yield and yield of upgraded coker gas oil products.
U.S. Pat. No. 7,303,664 refers to a process of delayed coking for making substantially free-flowing coke, preferably shot coke. in this process feedstock based on vacuum residuum, is heated in a heating zone to coking temperatures then conducted to a coking zone wherein volatiles are collected overhead and coke is formed. A metals-containing additive is added to the feedstock prior to it being heated in the heating zone.
U.S. Pat. No. 7,374,665 is concerning a method of blending delayed coker feedstocks to produce a coke that is easier to remove from a coker drum. A first feedstock is selected having less than about 250 wppm dispersed metals content and greater than about 5.24 API (American Petroleum Institute) gravity. A second delayed coker feedstock is blended with said first resid feedstock so that the total dispersed metals content of the blend will be greater than about 250 wppm and the API gravity will be less than about 5.24.
U.S. Pat. Nos. 7,658,838, & 7,645,735 relate to a delayed coking process for making substantially free-flowing coke, preferably shot coke from vacuum residuum with the help of addition of about 300 to about 3,000 wppm of polymeric additive.
U.S. Pat. No. 7,914,668 refers to a thermal conversion process for continuously producing hydrocarbon vapor and continuously removing a free-flowing coke. The coke, such as a shot coke, can be withdrawn continuously via, e.g., a staged lock hopper system.
U.S. Pat. No. 8,147,676 relates to an improved delayed coking process in which coker feed, such as a vacuum resid, is treated with (i) a metal-containing agent and (ii) an oxidizing agent. The feed is treated with the oxidizing agent at an oxidizing temperature. The oxidized feed is then pre-heated to coking temperatures and conducted to a coking vessel for a coking time to allow volatiles to evolve and to produce a substantially free-flowing coke. A metals-containing composition is added to the feed prior to the heating of the feed to coking temperatures.
The process disclosed in U.S. Pat. No. 8,105,482 reduces the viscosity of feedstock in order to permit the pipeline transport of upgraded feedstock with little or no addition of diluents. The process refers to pyrolysis in order to upgrade the viscosity of oil. Heat carrier is silica sand. This patent discloses ex situ regeneration of catalyst/heat carrier. Residence time is 2 s. Feed contains emulsion in water along with surfactants. It is oil/water emulsion with feed containing tar sand, bitumen, etc. at having at least 20 wt % CCR. Ratio of heat carrier to feed is high 10:1 to 200:1 and the process is Fixed bed process.
U.S. Pat. No. 8,206,574 refers to a reactor process added to a coking process to modify the quantity or yield of a coking process involving delayed coking, fluid coking, flexicoking, or other coking processes with additive comprising catalyst(s), seeding agent(s), excess reactant(s), quenching agent(s), carrier fluid(s), Which may alumina, silica, zeolite, calcium compounds, iron compounds, activated carbon, crushed pet coke in addition new catalyst, FCCU equilibrium catalyst, spent catalyst, regenerated catalyst. In the prior art process, some of the catalytic materials posses high acidic bronsted sites in case involvement of zeolitic materials which causes over cracking besides imposing limitation in strippability of unreacted feed and product molecules trapped in zeolite pores. Further, alumina & silica based material do not offer adequate sites for inducing cracking. There is a need within the art for a rapid and effective upgrading process of a heavy oil or bitumen feedstock that involves a high heat carrier incorporated with weak acid sites to obtain a product rich in liquid over the starting material. Ideally this process would be able to accommodate feedstocks comprising significant amounts of Feed CCR, Metal (Ni &V) and Asphaltenes.
From the various prior art coking processes it can be seen that, Fluid coking and Flexi coking processes are the dynamic and continuous while, delayed coker is a batch process. In the Fluid/Flexi coking volatile combustion matter can be brought in the range 4-10wt %, and this process has limitation in carrying required heat for sustaining endothermic cracking, vaporization reaction as well as providing required adequate strength acid sites. Though U.S. Pat. No. 8,206,574 refers to a coking process to modify the quantity or yield of a coking process involving additive comprising catalyst(s), seeding agent(s), excess reactant(s), quenching agent(s), carrier fluid(s), which may alumina, silica, zeolite, calcium compounds, iron compounds, activated carbon, crushed pet coke in addition new catalyst, FCCU equilibrium catalyst, spent catalyst, regenerated catalyst but is silent on type and strength of acid sites needed and their preparation.